Cured silicone microparticles are used, for example, as surface lubricants for organic resin films and as internal stress-relieving agents for thermosetting resins. In one method known for the preparation of cured silicone microparticles, a water-based suspension of cured silicone microparticles is prepared by curing a curable liquid silicone composition while said composition is emulsified in water (refer to Japanese Patent Application Laid Open Number Sho 63-77942 (77,942/1988), Japanese Patent Application Laid Open Number Sho 64-70558 ( 70,558/1989 ) and Japanese Patent Application Laid Open Number Sho 63-309565 (309,565/1988)). In this method, however, there is a strong tendency for the cured silicone microparticles to aggregate or agglomerate during removal of the water from the water-based suspension of the cured silicone microparticles. As a result, a drawback to this method is the formation of aggregates among the primary cured silicone microparticles. This type of cured silicone micropowder has heretofore been blended into organic resins by, for example, the following methods:
(a) the cured silicone microparticles are re-comminuted and blended into the organic resin; PA1 (b) a homogeneous powder mixture-is first prepared by mixing the cured silicone microparticles with inorganic microparticles that are also to be blended into the organic resin, and this powder mixture is subsequently blended into the organic resin. PA1 (A) cured silicone microparticles having an average particle diameter of 0.1 to 200 micrometers; PA1 (B) inorganic microparticles having an average particle diameter of 0.1 to 200 micrometers; and optionally, PA1 (C) surfactant.
These methods for blending the prior cured silicone micropowders into organic resins have required either a device for re-comminuting the cured silicone microparticles or a mixing device for the purpose of preliminarily mixing the cured silicone microparticles and inorganic microparticles. Moreover, substantial time and labor inputs have been required in order to obtain a homogeneous mixture of the cured silicone microparticles and inorganic microparticles.
The present patent applicant has already proposed a method for preparing a cured silicone microparticle whose surface is coated with inorganic microparticles (refer to Japanese Patent Application Number Hei 3-151099. The cured silicone microparticles afforded by the preparative method proposed in Japanese Patent Application Number Hei 3-151099 do in fact have an excellent flowability. However, because inorganic microparticles blanket the surface of this cured silicone microparticle, the blends of such a product with organic resins can suffer from an attenuated interaction between the cured silicone and organic resin.